Factors increasing the risk (to either the woman, the fetus/es, or both) of pregnancy complications beyond the normal level of risk may be present in a woman's medical profile either before she becomes pregnant or during the pregnancy. These pre-existing factors may relate to physical and/or mental health, and/or to social issues, or a combination.

Some common risk factors include:

- Age of either parent

- Adolescent parents

- Older parents

- Exposure to environmental toxins in pregnancy

- Exposure to recreational drugs in pregnancy:

- Ethanol during pregnancy can cause fetal alcohol syndrome and fetal alcohol spectrum disorder.

- Tobacco smoking and pregnancy, when combined, causes twice the risk of premature rupture of membranes, placental abruption and placenta previa. Also, it causes 30% higher odds of the baby being born prematurely.

- Prenatal cocaine exposure is associated with, for example, premature birth, birth defects and attention deficit disorder.

- Prenatal methamphetamine exposure can cause premature birth and congenital abnormalities. Other investigations have revealed short-term neonatal outcomes to include small deficits in infant neurobehavioral function and growth restriction when compared to control infants. Also, prenatal methamphetamine use is believed to have long-term effects in terms of brain development, which may last for many years.

- Cannabis in pregnancy is possibly associated with adverse effects on the child later in life.

- Exposure to Pharmaceutical drugs in pregnancy. Anti-depressants, for example, may increase risks of such outcomes as preterm delivery.

- Ionizing radiation

- Risks arising from previous pregnancies:

- Complications experienced during a previous pregnancy are more likely to recur.

- Many previous pregnancies. Women who have had five previous pregnancies face increased risks of very rapid labor and excessive bleeding after delivery.

- Multiple previous fetuses. Women who have had more than one fetus in a previous pregnancy face increased risk of mislocated placenta.

- Multiple pregnancy, that is, having more than one fetus in a single pregnancy.

- Social and socioeconomic factors. Generally speaking, unmarried women and those in lower socioeconomic groups experience an increased level of risk in pregnancy, due at least in part to lack of access to appropriate prenatal care.

- Unintended pregnancy. Unintended pregnancies preclude preconception care and delays prenatal care. They preclude other preventive care, may disrupt life plans and on average have worse health and psychological outcomes for the mother and, if birth occurs, the child.

- Height. Pregnancy in women whose height is less than 1.5 meters (5 feet) correlates with higher incidences of preterm birth and underweight babies. Also, these women are more likely to have a small pelvis, which can result in such complications during childbirth as shoulder dystocia.

- Weight

- Low weight: Women whose pre-pregnancy weight is less than 45.5 kilograms (100 pounds) are more likely to have underweight babies.

- Obese women are more likely to have very large babies, potentially increasing difficulties in childbirth. Obesity also increases the chances of developing gestational diabetes, high blood pressure, preeclampsia, experiencing postterm pregnancy and/or requiring a cesarean delivery.

- Intercurrent disease in pregnancy, that is, a disease and condition not necessarily directly caused by the pregnancy, such as diabetes mellitus in pregnancy, SLE in pregnancy or thyroid disease in pregnancy.

Some disorders and conditions can mean that pregnancy is considered high-risk (about 6-8% of pregnancies in the USA) and in extreme cases may be contraindicated. High-risk pregnancies are the main focus of doctors specialising in maternal-fetal medicine.

Serious pre-existing disorders which can reduce a woman's physical ability to survive pregnancy include a range of congenital defects (that is, conditions with which the woman herself was born, for example, those of the heart or , some of which are listed above) and diseases acquired at any time during the woman's life.

Intrauterine exposure to environmental toxins in pregnancy has the potential to cause adverse effects on the development of the embryo/fetus and to cause pregnancy complications. Air pollution has been associated with low birth weight infants. Conditions of particular severity in pregnancy include mercury poisoning and lead poisoning. To minimize exposure to environmental toxins, the "American College of Nurse-Midwives" recommends: checking whether the home has lead paint, washing all fresh fruits and vegetables thoroughly and buying organic produce, and avoiding cleaning products labeled "toxic" or any product with a warning on the label.

Pregnant women can also be exposed to toxins in the workplace, including airborne particles. The effects of wearing N95 filtering facepiece respirators are similar for pregnant women as non-pregnant women, and wearing a respirator for one hour does not affect the fetal heart rate.

A pregnant woman may have intercurrent diseases, defined as disease not directly caused by the pregnancy, but that may become worse or be a potential risk to the pregnancy.

- Diabetes mellitus and pregnancy deals with the interactions of diabetes mellitus (not restricted to gestational diabetes) and pregnancy. Risks for the child include miscarriage, growth restriction, growth acceleration, fetal obesity (macrosomia), polyhydramnios (too much amniotic fluid), and birth defects.

- Thyroid disease in pregnancy can, if uncorrected, cause adverse effects on fetal and maternal well-being. The deleterious effects of thyroid dysfunction can also extend beyond pregnancy and delivery to affect neurointellectual development in the early life of the child. Demand for thyroid hormones is increased during pregnancy which may cause a previously unnoticed thyroid disorder to worsen.

- Untreated celiac disease can cause spontaneous abortion (miscarriage), intrauterine growth restriction, small for gestational age, low birthweight and preterm birth. Often reproductive disorders are the only manifestation of undiagnosed celiac disease and most cases are not recognized. Complications or failures of pregnancy cannot be explained simply by malabsorption, but by the autoimmune response elicited by the exposure to gluten, which causes damage to the placenta. The gluten-free diet avoids or reduces the risk of developing reproductive disorders in pregnant women with celiac disease. Also, pregnancy can be a trigger for the development of celiac disease in genetically susceptible women who are consuming gluten.

- Systemic lupus erythematosus in pregnancy confers an increased rate of fetal death "in utero," spontaneous abortion, and of neonatal lupus.

- Hypercoagulability in pregnancy is the propensity of pregnant women to develop thrombosis (blood clots). Pregnancy itself is a factor of hypercoagulability (pregnancy-induced hypercoagulability), as a physiologically adaptive mechanism to prevent "post partum" bleeding. However, in combination with an underlying hypercoagulable states, the risk of thrombosis or embolism may become substantial.

Advanced maternal age is associated with adverse outcomes in the perinatal period, which may be caused by detrimental effects on decidual and placental development.

The risk of the mother dying before the child becomes an adult increases by more advanced maternal age, such as can be demonstrated by the following data from France in 2007:

Advanced maternal age continues to be associated with a range of adverse pregnancy outcomes including low birth weight, pre-term birth, stillbirth, unexplained fetal death, and increased rates of Caesarean section.

On the other hand, advanced maternal age is associated with a more stable family environment, higher socio-economic position, higher income and better living conditions, as well as better parenting practices, but it is more or less uncertain whether these entities are "effects" of advanced maternal age, are "contributors" to advanced maternal age, or common effects of a certain state such as personality type.

A uterine scar from a previous cesarean section is the most common risk factor. (In one review, 52% had previous cesarean scars.) Other forms of uterine surgery that result in full-thickness incisions (such as a myomectomy), dysfunctional labor, labor augmentation by oxytocin or prostaglandins, and high parity may also set the stage for uterine rupture. In 2006, an extremely rare case of uterine rupture in a first pregnancy with no risk factors was reported.

Kalberer et al. have shown that despite the older maternal age at birth of the first child, the time span between the birth of the first and the second child (= interpregnancy interval) decreased over the last decades. If purely biological factors were at work, it could be argued that interpregnancy interval should have increased, as fertility declines with age, which would make it harder for the woman to get a second child after postponed birth of the first one. This not being the case shows that sociologic factors (see above) prime over biological factors in determining interpregnancy interval.

With technology developments cases of post-menopausal pregnancies have occurred, and there are several known cases of older women carrying a pregnancy to term, usually with in vitro fertilization of a donor egg. A 61-year-old Brazilian woman with implantation of a donor egg expected gave birth to twins in October 2011..

Emergency exploratory laparotomy with cesarean delivery accompanied by fluid and blood transfusion are indicated for the management of uterine rupture. Depending on the nature of the rupture and the condition of the patient, the uterus may be either repaired or removed (cesarean hysterectomy). Delay in management places both mother and child at significant risk.

Rarely, a sharply tilted uterus is due to a disease such as endometriosis, an infection or prior surgery. Although this may make it more challenging for the sperm to reach the egg, conception can still occur. A tipped uterus will usually right itself during the 10th to 12th week of pregnancy. Rarely (1 in 3000 to 8000 pregnancies) a tipped uterus will cause painful and difficult urination, and can cause severe urinary retention. Treatment for this condition (called "incarcerated uterus") includes manual anteversion of the uterus, and usually requires intermittent or continuous catheter drainage of the bladder until the problem is rectified or spontaneously resolves by the natural enlargement of the uterus, which brings it out of the tipped position. In addition to manual anteversion and bladder drainage, treatment of urinary retention due to retroverted uterus can require the use of a pessary, or even surgery, but often is as simple as having the pregnant mother sleep on her stomach for a day or two, to allow the retroverted uterus to move forward.

If a uterus does not right itself, it may be labeled "persistent".

Methods of measuring blood loss associated with childbirth vary, complicating comparison of prevalence rates. A systematic review reported the highest rates of PPH in Africa (27.5%), and the lowest in Oceania (7.2%), with an overall rate globally of 10.8%. The rate in both Europe and North America was around 13%. The rate is higher for multiple pregnancies (32.4% compared with 10.6% for singletons), and for first-time mothers (12.9% compared with 10.0% for women in subsequent pregnancies). The overall rate of severe PPH (>1000 ml) was much lower at an overall rate of 2.8%, again with the highest rate in Africa (5.1%).

Causes of postpartum hemorrhage are uterine atony, trauma, retained placenta, and coagulopathy, commonly referred to as the "four Ts":

- Tone: uterine atony is the inability of the uterus to contract and may lead to continuous bleeding. Retained placental tissue and infection may contribute to uterine atony. Uterine atony is the most common cause of postpartum hemorrhage.

- Trauma: Injury to the birth canal which includes the uterus, cervix, vagina and the perineum which can happen even if the delivery is monitored properly. The bleeding is substantial as all these organs become more vascular during pregnancy.

- Tissue: retention of tissue from the placenta or fetus may lead to bleeding.

- Thrombin: a bleeding disorder occurs when there is a failure of clotting, such as with diseases known as coagulopathies.

For most women, PGP resolves in weeks after delivery but for some it can last for years resulting in a reduced tolerance for weight bearing activities. PGP can take from 11 weeks, 6 months or even up to 2 years postpartum to subside. However, some research supports that the average time to complete recovery is 6.25 years, and the more severe the case is, the longer recovery period.

Overall, about 45% of all pregnant women and 25% of all women postpartum suffer from PGP. During pregnancy, serious pain occurs in about 25%, and severe disability in about 8% of patients. After pregnancy, problems are serious in about 7%. There is no correlation between age, culture, nationality and numbers of pregnancies that determine a higher incidence of PGP.

If a woman experiences PGP during one pregnancy, she is more likely to experience it in subsequent pregnancies; but the severity cannot be determined.

Neonatal milk or witch's milk is milk secreted from the breasts of approximately 5% of newborn infants. It is considered a normal variation and no treatment or testing is necessary. In folklore, witch's milk was believed to be a source of nourishment for witches' familiar spirits.

In most cases, a retroverted uterus is genetic and is perfectly normal but there are other factors that can cause the uterus to be retroverted. Some cases are caused by pelvic surgery, pelvic adhesions, endometriosis, fibroids, pelvic inflammatory disease, or the labor of childbirth.

In vitro fertilisation is a process by which an egg is fertilised by sperm outside the body: "in vitro". IVF is a major treatment for infertility when other methods of assisted reproductive technology have failed. The process involves monitoring a woman's ovulatory process, removing ovum or ova (egg or eggs) from the woman's ovaries and letting sperm fertilise them in a fluid medium in a laboratory. When a woman's natural cycle is monitored to collect a naturally selected ovum (egg) for fertilisation, it is known as natural cycle IVF. The fertilised egg (zygote) is then transferred to the patient's uterus with the intention of establishing a successful pregnancy.

While IVF therapy has largely replaced tubal surgery in the treatment of infertility, the presence of hydrosalpinx is a detriment to IVF success. It has been recommended that prior to IVF, laparoscopic surgery should be done to either block or remove hydrosalpinges.

One reason that poverty produces such high rates of fistula cases is the malnutrition that exists in such areas. Lack of money and access to proper nutrition, as well as vulnerability to diseases that exist in impoverished areas because of limited basic health care and disease prevention methods, cause inhabitants of these regions to experience stunted growth. Sub-Saharan Africa is one such environment where the shortest women have on average lighter babies and more difficulties during birth when compared with full-grown women. This stunted growth causes expectant mothers to have skeletons unequipped for proper birth, such as an underdeveloped pelvis. This weak and underdeveloped bone structure increases the chances that the baby will get stuck in the pelvis during birth, cutting off circulation and leading to tissue necrosis. Because of the correlation between malnutrition, stunted growth, and birthing difficulties, maternal height can at times be used as a measure for expected labor difficulties.

High levels of poverty also lead to low levels of education among impoverished women concerning maternal health. This lack of information in combination with obstacles preventing rural women to easily travel to and from hospitals lead many to arrive at the birthing process without prenatal care. This can cause a development of unplanned complications that may arise during home births, in which traditional techniques are used. These techniques often fail in the event of unplanned emergencies, leading women to go to hospital for care too late, desperately ill, and therefore vulnerable to the risks of anesthesia and surgery that must be used on them. In a study of women who had prenatal care and those who had unbooked emergency births, “the death rate in the booked-healthy group was as good as that in many developed countries, [but] the death rate in the unbooked emergencies was the same as the death rate in England in the 16th and 17th centuries.” In this study, 62 unbooked emergency women were diagnosed with obstetric fistulae out of 7,707 studied, in comparison to three diagnosed booked mothers out of 15,020 studied. In addition, studies find that education is associated with lower desired family size, greater use of contraceptives, and increased use of professional medical services. Educated families are also more likely to be able to afford health care, especially maternal healthcare.

The most common cause is the mismanagement of 3rd stage of labor, such as:

- Fundal pressure

- Excess cord traction during the 3rd stage of labor

Other natural causes can be:

- Uterine weakness, congenital or not

- Precipitate delivery

- Short umbilical cord

It is more common in multiple gestation than in singleton pregnancies.

The incidence is of 1/2000 pregnancies.

Galactorrhea can take place as a result of dysregulation of certain hormones. Hormonal causes most frequently associated with galactorrhea are hyperprolactinemia and thyroid conditions with elevated levels of thyroid-stimulating hormone (TSH) or thyrotropin-releasing hormone (TRH). No obvious cause is found in about 50% of cases.

Lactation requires the presence of prolactin, and the evaluation of galactorrhea includes eliciting a history for various medications or foods (methyldopa, opioids, antipsychotics, serotonin reuptake inhibitors, as well as licorice) and for behavioral causes (stress, and breast and chest wall stimulation), as well as evaluation for pregnancy, pituitary adenomas (with overproduction of prolactin or compression of the pituitary stalk), and hypothyroidism. Adenomas of the anterior pituitary are most often prolactinomas. Overproduction of prolactin leads to cessation of menstrual periods and infertility, which may be a diagnostic clue. Galactorrhea may also be caused by hormonal imbalances owing to birth control pills.

Galactorrhea is also a side effect associated with the use of the second-generation H receptor antagonist cimetidine (Tagamet). Galactorrhea can also be caused by antipsychotics that cause hyperprolactinemia by blocking dopamine receptors responsible for control of prolactin release. Of these, risperidone is the most notorious for causing this complication. Case reports suggest proton-pump inhibitors have been shown to cause galactorrhea.

Uterine inversion is often associated with significant Post-partum hemorrhage. Traditionally it was thought that it presented with haemodynamic shock "out of proportion" with blood loss, however blood loss has often been underestimated. The parasympathetic effect of traction on the uterine ligaments may cause bradycardia.

There are many causes of "fetal distress" including:

- Breathing problems

- Abnormal position and presentation of the fetus

- Multiple births

- Shoulder dystocia

- Umbilical cord prolapse

- Nuchal cord

- Placental abruption

- Premature closure of the fetal ductus arteriosus

- Uterine rupture

- Intrahepatic cholestasis of pregnancy, a liver disorder during pregnancy

In 2013 it resulted in 19,000 maternal deaths down from 29,000 deaths in 1990.

Most commonly a tube may be obstructed due to infection such as pelvic inflammatory disease (PID). The rate of tubal infertility has been reported to be 12% after one, 23% after two, and 53% after three episodes of PID. The Fallopian tubes may also be occluded or disabled by endometritis, infections after childbirth and intraabdominal infections including appendicitis and peritonitis. The formation of adhesions may not necessarily block a fallopian tube, but render it dysfunctional by distorting or separating it from the ovary. It has been reported that women with distal tubal occlusion have a higher rate of HIV infection.

Fallopian tubes may be blocked as a method of contraception. In these situations tubes tend to be healthy and typically patients requesting the procedure had children. Tubal ligation is considered a permanent procedure.

If cesarean section is obtained in a timely manner, prognosis is good. Prolonged obstructed labour can lead to stillbirth, obstetric fistula, and maternal death.

The underlying cause of the rapidly growing breast connective tissue, resulting in gigantic proportions, has not been well-elucidated. However, proposed factors have included increased levels/expression of or heightened sensitivity to certain hormones (e.g., estrogen, progesterone, and prolactin) and/or growth factors (e.g., hepatic growth factor, insulin-like growth factor 1, and epidermal growth factor) in the breasts. Macromastic breasts are reported to be composed mainly of adipose and fibrous tissue, while glandular tissue remains essentially stable.

Macromastia occurs in approximately half of women with aromatase excess syndrome (a condition of hyperestrogenism). Hyperprolactinemia has been reported as a cause of some cases of macromastia. Macromastia has also been associated with hypercalcemia (which is thought to be due to excessive production of parathyroid hormone-related protein) and, rarely, systemic lupus erythematosus and pseudoangiomatous stromal hyperplasia. It is also notable that approximately two-thirds of women with macromastia are obese. Aside from aromatase (as in aromatase excess syndrome), at least two other genetic mutations (one in PTEN) have been implicated in causing macromastia.

A handful of drugs have been associated with gigantomastia, including penicillamine, bucillamine, neothetazone, ciclosporin, and indinavir.